Voice messaging systems generally have remained substantially unchanged over the past few decades. The systems are typically incapable of allowing message recipients to reply to message senders unless the sender and the recipient each share the same voice messaging platform (such as in, for example, enterprise systems in a corporate environments).
Further, mobile and fixed-line voice messaging systems are typically independent and do not interoperate. Thus, message recipients cannot reply to message senders. In order to facilitate asynchronous voice messaging, the recipients must discontinue message retrieval sessions and place a separate out-going call to the sender. The recipient can then either communicate directly with the sender or reach the sender's voice messaging system where the recipient is only then able to leave a reply message.
Asynchronous messaging can be further enhanced by message threading. Typically, only closed messaging systems (such as the enterprise system discussed above) provide message threading. Open messaging systems such as those provided by consumer fixed and mobile service providers (i.e., telephony service carriers) are unable to reply across system domains or to thread replies.